Although the invention is applicable to any pipelines, the present invention and the set of problems on which it is based are explained in greater detail in the following by way of a pipeline for emptying a waste water tank of an aeroplane.
In modern commercial aeroplanes, waste water tanks are required for collecting waste water from the toilets, washbasins and the like which are located on board. A waste water tank of this type may for example be arranged inside the aircraft fuselage between a floor structure and a fuselage outer skin, and be mounted on the fuselage structure.
Orderly emptying of a waste water tank of this type should be provided during the idle time of the aeroplane on the ground. For this purpose, the waste water tank is provided with a pipeline, for example in the lower region thereof. This pipeline connects the waste water tank to what is known as the “waste service panel”, a means which is conventionally arranged in the region of the outer skin and arranged substantially immovably in relation thereto, and which makes orderly emptying of the waste water tank possible. While the aircraft is located on the ground, the “waste service panel” for emptying the waste water tank is accessible from the outside of the aeroplane fuselage. A valve, to which the pipeline is coupled, and by means of which the escape of liquid from the waste water tank through the pipeline can be prevented or released, may be arranged on this “waste service panel”.
During flight, however, the fuselage of a modern commercial aeroplane does not behave as a completely rigid body, but is subject in a known manner to deformation, known as “blowback”, of the fuselage, predominantly when cruising at high altitudes, as a result of air pressure differences between the respective part of the fuselage internal space and the surrounding atmosphere. Cooling of the fuselage structure, as a result of the low air temperatures in the surrounding atmosphere at flight altitudes, also has an influence on the deformation of the fuselage. Further, flight manoeuvres, which are brought about in particular by rudder deflections, also contribute to a deformation and/or distortion of the aeroplane fuselage.
At the conventional size of the waste water tank which is mounted on the structure, it is thus possible for a relative movement and thus a non-negligible displacement and/or angular offset of the pipeline which empties the tank to occur, relative to the “waste service panel” and the valve which is fastened thereto, by comparison with the state of the aeroplane when located on the ground. These relative movements have to be taken into account so as to ensure tightness of the coupling of the pipeline to the valve in the event of relative movements of this type in regular flight operation.
Against this background, an idea of the present invention is to provide a movable coupling for a pipeline which makes it possible to compensate relative movements of this type and at the same time requires as little space as possible.